For the purposes of the instant application, an electrical contact refers to an electro-mechanical device that may be employed when it is desired to readily connect (or disconnect) a first-insulated conductor to (or from) a second insulated conductor. Such a device is included, for example, in a conventional telephone circuit wire connector or in a conventional telephone electrical termination block of the type that provides telephone service to a customer.
In order to explain how an electrical contact is included in a telephone electrical termination block, attention is directed to FIG. 1 which shows a typical termination block 10. The termination block 10 includes a plurality of binding posts 12 which are, in fact, the electrical contacts. The binding posts 12 each comprise a small screw-type contact that facilitates the connection or disconnection of the first and second insulated conductors. Here, the first conductor may comprise a drop or service wire 14 that is wrapped around the screw-type contact so as to provide a connection between the customer and the termination block 10. The second conductor, on the other hand, may comprise a cable stub 16 which is pre-wired to a hermetically sealed portion of the termination block 10.
Although an end lead of the cable stub 16 is hermetically sealed within a portion of the termination block 10, the binding posts 12 (which connect one end of the service wire 14) may be exposed to the outside environment. The binding posts 12 are typically kept in this exposed condition in order to facilitate a craftsperson's reentry to the termination block 10 in order to effect repairs or change a service connection.
If the binding posts 12 remain exposed but unprotected from the outside environment, they may be affected by environmental agents including dirt, plant life, moisture, corrosion deposits and insects. These agents, however, can be adversative to the termination block 10 because they may effect a conductive bridge between some or all of the binding post contacts. This conductive bridge, in turn, may provide a means for the creation of noise and may produce an electrical short-circuit within the termination block. It is noted in particular, that such termination blocks that are left unprotected within humid or moist environments can incur a critical loss of insulation resistance between binding post contacts which can result in a temporary or permanent disruption of termination block operation or customer service.
In order to avoid disruption of service, therefore, it is important that the termination block be maintained so that it is resistant to the cited adverse environmental agents and can remain moisture insensitive. Consequently, it is important that the binding post contacts (or electrical contacts) be provided with a protection means (of the type indicated generally by numeral 18 in FIG. 1) that insures their reliable and safe operation within an otherwise adverse and moisture-laden environment.
In order to select an appropriate protection means for electrical contacts, it is advantageous to realize the following design objectives. Thus, the protection means should not obstruct or delay a craftsperson's access to the reenterable electrical contacts. At the same time, and as its name suggests, the protection means should protect the electrical contacts from the above described adverse environmental agents, including a high humidity environment. To these design objective ends, it is advantageous that the protection means utilize materials that are non-hazardous, possess acceptable electrical properties including a desired insulation resistance and remain substantially inert toward a molded plastic substrate which typically houses the electrical contacts.
The prior art addresses these stated design objectives by recourse to, for example, powders, foams, plastic gaskets, grease caulking guns and "hot-pour" liquids that cure in situ. These prior art protection means do not, however, in an entirely satisfactory manner, meet the required design objectives. Notably, as exemplified by the disclosure entitled Two-Part Reactive Dielectric Filler Composition in the U.S. Pat. No. 4,102,716 to Graves, et al., the hot-pour liquid composition must be formed by pouring it into a closure containing insulating conductors and then waiting for a delay period of upwards of two hours for the composition to gel or cure. Other illustrative disclosures, like that of U.S. Pat. No. 3,897,129 to Farrar, Jr., leave a careful reader with an unclear idea as to how a craftspreson can make numerable reentrys to the electrical contacts while insuring that a protective agent (here, grease) is always adequately applied to the electrical contacts. The cited inadequacies of these prior art disclosures suggest that a need exists for a protection means for electrical contacts that is responsive to the enumerated difficulties and satisfies the aforementioned design objectives.
The present invention fulfills this need and satisfies the design objectives by providing a unique apparatus and method for protection of electrical contacts. The apparatus of the present invention does not obstruct or delay a craftsperson's repeated reentrys to the electrical contact. At the same time, the present invention safely protects the electrical contacts even when they are exposed to an adverse environment. The present invention may consequently be employed with a variety of electro-mechanical devices like connectors or termination blocks where it is important to have ready access to the device while insuring, nevertheless, that the device is protected from the adverse environment.